1. Technical Field
The present invention relates to toner, which is utilized in such as a printer, a copying machine and a facsimile, as well as toner images comprising which can be fixed at a low temperature, and a manufacturing method thereof.
2. Related Art
In the field of electrophotographic technologies of such as a copying machine and a printer, in accordance with development of digital technologies in recent years, image formation of high precision and high resolution, such as to accurately visualize dot images comprising as minute as a 1200 dpi (dpi represents a dot number per 1 inch or per 2.54 cm) level, has been required. To achieve such image formation of high precision and high resolution, minimization of a toner particle diameter has been also in progress, and, for example, remarkable is development of a minimization technique of the particle diameter by means of chemical toner represented by polymer toner.
By the way, when particle size minimization of toner proceeds, there is caused a tendency that a deviation in a charging property of toner particles is liable to be generated, and to make a uniform charging property of toner particles, for example, polyester resin is prepared from polycarboxylic acids or polyhydric alcohols which are provided with a polymerizing double bond in their structure, resulting in a toner technique containing said resin (refer to patent literature 1).
On the other hand, in view of energy saving, development of toner capable of being fixed at a low temperature has been made. For example, listed is a development of toner which exhibit a low temperature fixing ability by utilizing a vinyl type copolymer, provided with an acid group and a hydroxyl group, as binder resin, and taking measures such as adjusting a molecular weight distribution and a cross-linking structure formation or performing the resin design of a molecular chain structure corresponding to the molecular weight (refer to patent literature 2).
Further, there is listed development of toner to achieve low temperature fixing by utilizing a binder resin which is comprised of, urethane modified polyol resin utilizing polyisocyanate, and styrene type copolymer resin constituted of an acrylic acid ester type monomer or an methacrylic type monomer as a constituent unit (for example, refer to patent literature 3).
By the way, needs of energy saving for an image forming apparatus has been existing since olden times, however, recently, further higher become the needs of energy saving in an image forming apparatus.
This is considered to be because of significant change of a using style of copying machine and a printer, in particular, recently. For example, in an office, several sets of printers in each section have come to be utilized in connection to a LAN, and to decrease electricity consumption per an individual printer has come to be an important problem also in view of prevention of warming up of the earth in addition to achieving a comfortable working place and decreasing electricity cost.
In this way, toner capable of exhibiting stable fixing ability at a low temperature has been required, with respect to energy saving, operating environment of a user, as well as in view of global environment, however, it is necessary to set a low glass transition temperature of resin to enable stable fixing at low temperatures (for example, at a temperature lower than a boiling point of water).
However, when a glass transition temperature of resin is set lower, there is a tendency of toner particles to adhere or aggregate with each other resulting in difficulty of exhibiting a stable storage quality.
Further, in the case that binder resin or a releasing agent exhibiting a crystallizing property are contained in toner, decrease of glossiness and gloss unevenness of images are observed, which is estimated because of progress of crystallization even at a low temperature, resulting in an obstacle to form a printed image provided with beautiful finish.
Therefore, low temperature fixing toner has been required to be provided with not only a fixing ability but also storage stability not causing aggregation even in long term storage. Further, the formed toner image is required to have a fixing ability as well as beautiful finish without unevenness.
Further, recently, image technology of electrophotographic method is attracting attention in the field of small volume printing due to a merit of no troublesome to specifically prepare a plate, and has been applied for an image forming method of a print-on-demand mode which provides as many copies as required to reply a small scale order.
In such a printing application, since the types of paper utilized for image formation increase significantly compared to the application in the case of conventional copying machine or a printer, it is required to form toner images for every type of paper. However, it has been difficult to stably form toner images for every type of paper with present toner. Further, since the temperature at the time of fixing provides not a small effect on the fiber constituting paper, development of toner fixable at a lower temperature has been desired also in the case of being utilized in a small scale printing application.
[Patent literature 1] JP-A No. 2003-5441 (Hereinafter, JP-A refers to Japanese Patent Publication Open to Public Inspection.)
[Patent literature 2]JP-A No. 2003-57877[Patent literature 3]JP-A No. 2004-20575